Depressional wetlands in the Columbia Plateau are valuable habitats because they maintain surface water into or throughout the dry summers. The source of that moisture—surface runoff from surrounding areas, or groundwater in local aquifers—may determine if these wetlands are seasonal, permanent, or semi-permanent. Helping these wetlands continue to provide habitat and other services requires understanding how these flooding and drying patterns (their hydrology) have changed in the past, and how projected changes in climate might affect them. The goal of this project was to develop wall-to-wall maps of wetlands across the region, coupled with detailed 30-year hydrographs of historical (1984-2014) fluctuations in water extent for each wetland, and similar 30-year hydrographs for fluctuations expected under future (2070-2099) climate. We developed these products using Landsat satellite images to map surface water extent of wetlands. We then combined these data with VIC, a hydrological model that calculates soil moisture metrics given particular climate data. We quantified the relationships between surface water extent and the VIC metrics produced using historical climate information. We then applied these relationships to soil moisture metrics obtained by running VIC using projected future climate, which allowed us to make projections of expected water extent under end-of-the-century climate. Our findings suggest that wetlands in the Columbia Plateau will respond differently across the region. Groundwater driven wetlands, which tend to be more permanently flooded, may see increases in water levels and dry less frequently. Surface water driven wetlands, which tend to be more seasonally flooded, may see decrease in surface water levels, dry more frequently, and dry earlier in the season. We worked with wetland practitioners to interpret the results, and to use them as part of a framework for evaluating whether current management actions could ameliorate expected climate change impacts.
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